Basic Information

Note: EPA no longer updates this information, but it may be useful for historical purposes. See http://www.epa.gov/airquality/powerplanttoxics/ for information about standards to limit mercury, acid gases and other toxic pollution from power plants.

On March 15, 2005, EPA issued a rule to permanently cap and reduce mercury emissions from coal-fired power plants.

The Clean Air Mercury Rule was built on EPA’s Clean Air Interstate Rule (CAIR) to significantly reduce emissions from coal-fired power plants -- the largest remaining sources of mercury emissions in the country. The goal of these rules regarding mercury was to reduce utility emissions of mercury from 48 tons a year to 15 tons, a reduction of nearly 70 percent.

The Clean Air Mercury Rule establishes “standards of performance” limiting mercury emissions from new and existing coal-fired power plants and creates a market-based cap-and-trade program to reduce nationwide utility emissions of mercury in two distinct phases. The first phase cap is 38 tons. In the second phase, due in 2018, coal-fired power plants will be subject to a second cap, which will reduce emissions to 15 tons upon full implementation.

New coal-fired power plants (“new” means construction starting on or after Jan. 30, 2004) will have to meet stringent new source performance standards in addition to being subject to the caps.

Mercury is a toxic, persistent pollutant that accumulates in the food chain. Mercury in the air is a global problem. While fossil fuel-fired power plants are the largest remaining source of human-generated mercury emissions in the United States.

The Clean Air Mercury Rule is expected to make reductions in emissions that are transported regionally and deposited domestically, and it will reduce emissions that contribute to atmospheric mercury worldwide.

Mercury and Fish

Concentrations of mercury in the air are usually low. However, atmospheric mercury falls to Earth through rain, snow and dry deposition and enters lakes, rivers and estuaries. Once there, it can transform into, methylmercury, and can build up in fish tissue.

Americans are exposed to methylmercury primarily by eating contaminated fish. Because the developing fetus is the most sensitive to the toxic effects of methylmercury, women of childbearing age are regarded as the population of greatest concern. Children who are exposed to methylmercury before birth may be at increased risk of poor performance on neurobehavioral tasks, such as those measuring attention, fine motor function, language skills, visual-spatial abilities and verbal memory.

Revison of December 2000 Finding

Also on March 15, 2005, in a separate but related action, EPA revised and reversed its December 2000 finding that it was “appropriate and necessary” to regulate coal- and oil-fired coal-fired power plants under section 112 of the Clean Air Act.

EPA has issued two complementary rules – CAIR and the Clean Air Mercury Rule, issued under sections 110(a)(2)(D) and 111 of the law, respectively. These rules will allow us to limit mercury emissions from these plants.

Cap and Trade Basics

The Clean Air Mercury Rule established a cap-and-trade system for mercury that is based on EPA’s proven Acid Rain Program. The Acid Rain Program has produced demonstrable results, reducing SO2 emissions faster and at far lower costs than anticipated, and resulting in wide-ranging environmental improvements.

In the Clean Air Mercury Rule, EPA has assigned each state and two tribes an emissions “budget” for mercury, and each state must submit a State Plan revision detailing how it will meet its budget for reducing mercury from coal-fired power plants. Two tribes that have coal-fired power plants that will be affected by this rule also have been assigned a mercury emissions budget.

The Clean Air Mercury Rule contained stringent emission monitoring and reporting requirements ensure that monitored data are accurate, that reporting is consistent among sources – and that the emission reductions occur.

For More Information

More information about mercury, EPA’s efforts to
reduce mercury emissions, and today’s rule is available at www.epa.gov/mercury.